Formation Of Concentric Rings Research Articles

Toxicity of Acephate to Liver and Kidney of Female Wistar Rats

Acephate is a broad spectrum insecticide used against pests of vegetables, cotton and ornamental plants. In the present study, acephate was orally administered to female wistar rats to examine its toxic effects, if any, at dose level of 1/50th, 1/25th and 1/10th of LD50 value along with a control group for 45 days. Results revealed a remarkable decrease in the feed intake of 1/10th acephate treated rats during 5th and 6th week of treatment. The net body weights and liver weight decreased non-significantly to a small extent over 45 days of treatment. The weight of kidney and content of total soluble protein decreased significantly in a dose dependent manner in treated rats. The significant alterations in the activity of antioxidative enzymes i.e. glutathione peroxidase, glutathione-S-transferase, glutathione reductase, superoxide dismutase, catalase and lipid peroxidation levels were observed. The appearance of comet in 1/10th dosed rats indicated DNA damage. Further, no formation of concentric rings in treated rats indicated the absence or low concentration of antibodies in the serum.

First report of Fusarium solani associated with the bulb rot of Tulip (Tulipa spp) in India.

Tulip is an ornamental bulbous flowering crop belonging to the Genus Tulipa and family Liliaceae. It is the first ranking bulbous ornamental plant in the world (Nayeem and Qayoom 2015). They are often the first flowers to witness the bloom in the spring. Kashmir valley is located in northern Himalayas in northwestern region of Indian subcontinent. It is the most alluring and fascinating place all over India and the home of famous "Indhra Gandhi Memorial Tulip garden", the largest tulip garden in the entire Asia. However there are number of constraints in tulip cultivation among which bulb rot occupy a prominent place (Piwoni 2000). Bulb rot is posing problem to all the tulip growers throughout the world (De Hertogh et al. 1983). Rot symptoms were observed on tulip bulbs in field as well as in storage conditions (20-22◦C temperature with a relative humidity of 65%) in the summers of 2018 and 2019 in Shalimar fields of Kashmir. The main disease symptoms are yellow sunken spots on bulbs, purple-yellow coloration of leaves. Causal agent was isolated using tissue bit technique (Pathak 1972) on potato dextrose agar plates which where incubated at 24±2◦C . Single spore technique was used to obtain the pure isolate (Johnston and Booth 1983). The isolate covered the full plate (90mm) in ten days. The colony was dull whitish in color, flat and smooth with concentric ring formation in the culture plate with inner ring having a creamy exudation. The mycelium was septate, branched and hyaline in color and measured 3.50-5.20 µm in width with an average of 4.4 µm. Micro-conidia were hyaline, cylindrical to oval, 0-1 septa and measured 7.50-11.00×2.80-3.75 µm in size. Macro conidia were hyaline with 3-4 septa, fusiform, moderately curved which measured 21.15- 32.00×3.80-4.75 µm in size with an average of 28.50±0.21× 4.30±0.2 µm. On the basis of these morphological and cultural characteristics of the fungus, it was identified as Fusarium solani (Mar.) Sacc.,. To confirm the identity the PCR amplification was carried out for two genes Internal Transcribed Spacer (ITS 1, ITS 4)and Translation Elongation factor1-alpha gene (tef1- alpha) (O'Donnell et al. 1998; White et al. 1990). BLAST analysis of the sequence obtained for both the genes showed 99% homology with F. solani sequences in GenBank and Fusarium -ID databases. The sequences were deposited in the GenBank (Accession No MN611433, MW995477). Pathogenicity test was conducted on variety orange emperor both in laboratory and polyhouse. Bulbs were divided into three sets, (three bulbs per set) one set was given injury and dipped in conidial suspension (106 conidia/ml) for 30 min, another set was kept uninjured and dipped in spore suspension of same concentration, the third set was served as control and dipped in sterilized distilled water. All the respective sets were incubated in a moist chamber maintained at a temperature of 22 ◦C to observe symptoms. The injured ones showed symptoms after 7-8 days of inoculation, whereas the uninjured bulbs showed symptoms after 11-12 days. No symptoms were observed in controlled set. A pot experiment was also conducted to carry the pathogenicity tests. Bulbs were injured with the help of sterile needle and were dipped in conidial suspension (106 conidia/ml) for 30 min (Pastrana et al. 2014). The bulbs kept for control were dipped in sterilized distilled water. Bulbs were then planted in pots maintained at 18◦C. The above ground parts of the inoculated bulbs showed symptoms like stunted growth which gradually turned yellow and did not produced flowers. The bulbs after harvesting were rotten .No symptoms were observed in controlled plants. To fulfill the Koch's postulates the fungal pathogen was re-isolated which was identified as F. solani. The pathogen is reported to cause disease in other crops (Gupta et al. 2012) but to our knowledge and on the basis of literature, this is the first report of F. solani causing bulb rot of tulip in India.

Orbital Angular Momentum from Self-Assembled Concentric Nanoparticle Rings.

Ring-shaped nanostructures can focus, filter, and manipulate electromagnetic waves, but are challenging to incorporate into devices using standard nanofabrication techniques. Directed self-assembly (DSA) of block copolymers (BCPs) on lithographically patterned templates has successfully been used to fabricate concentric rings and spirals as etching masks. However, this method is limited by BCP phase behavior and material selection. Here, a straightforward approach to generate ring-shaped nanoparticle assemblies in thin films of supramolecular nanocomposites is demonstrated. DSA is used to guide the formation of concentric rings with radii spanning 150-1150nm and ring widths spanning 30-60nm. When plasmonic nanoparticles are used, ring nanodevice arrays can be fabricated in one step, and the completed devices produce high-quality orbital angular momentum (OAM). Nanocomposite DSA simplifies and streamlines nanofabrication by producing metal structures without etching or deposition steps; it also introduces interparticle coupling as a new design axis. Detailed analysis of the nanoparticle ring assemblies confirms that the supramolecular system self-regulates the spatial distribution of its components, and thus exhibits a degree of flexibility absent in DSA of BCPs alone, where structures are determined by polymer-pattern incommensurability. The present studies also provide guidelines for developing self-regulating DSA as an alternative to incommensurability-driven methods.

Pattern formation in Passiflora incarnata: An activator-inhibitor model

Based on a careful examination of the onset of violet colored dots along the filaments in the developing floral bud stage and the formation of alternating bands of violet and white color in the matured flowers of Passiflora incarnata (Passion flower), it is concluded that the pattern arises from a competition between the production of violet colored anthocyanin and the colorless flavonols along the filaments. The activator-inhibitor model of Gierer and Meinhardt along with the reaction diffusion theory of Turing is used to explain the formation of concentric rings in the flower.

Confinement effect on spatio-temporal growth of spherulites from cellulose/ionic liquid solutions

In this study, we investigate the growth kinetics and through-the width-distribution of polycrystalline morphologies developed in the confined microcrystalline cellulose (MCC)/1-allyl-3-methylimidazolium chloride (AmimCl) solution films at controlled temperature and humidity. Being an anti-solvent, the diffusion of moisture from the edges to the interior of the cellulose film causes the aggregation and rearrangement of cellulose molecules. When the confined films of thickness varying between 100 μm and 850 μm are incubated for over 25 days, different polycrystalline morphologies evolve. While a skin-transition-core morphological distribution is observed in the films of thickness ≥ 700 μm, interesting morphologies such as cylindrites, shish-kebab, deformed spherulites are observed in confined films of thickness ≤ 500 μm. The formation of concentric rings called terraces is also observed on the spherulites in highly confined films, signaling two dimensional (2-D) growth. The growth kinetics is observed to follow the classical Avrami theory. The Avrami exponent value, n, in the highly confined film (100 μm) is found to be close to 2, indicating 2-D growth.

Wave mechanism of structure formation in cement compositions

The development of new methods of physicochemical analysis opens vast opportunities for studying the kinetics and mechanisms of the structure formation in cement systems. A study of the structure formation and cement hardening processes will allow widening a range of methods of their non-destructive testing and developing production techniques for advanced composite materials. The X-ray microtomography system is used to analyze the formation of alternating dark and bright concentric rings both on the surface and in the bulk of the specimens. It is supposed that the formation of concentric rings is caused by the generation of acoustic vibrations in the cement-water system at early stages of the structure formation.

A note on sensor arrangement for long-distance target localization

We considered a sensor formation problem for target localization based on the time difference of arrival (TDOA) data. It is assumed that the target is located far off from the sensors while the sensors are relatively close to each other. The estimators of the target location expressed in terms of the spherical coordinates are found to be uncorrelated when the sensors are arranged in a concentric ring formation. The proposed optimal formation of sensors is in the concentric ring formation and is shown to change in accordance with sensors' angular positions with respect to the line-of-sight vector from the reference sensor to the target. The proposed optimal sensor formations are compared in the context of estimation accuracy both in theory and by numerical experiments. They are shown optimal in general through refined numerical experiments.

Interference rings formation inside cellulose from a back-reflected femtosecond laser pulse

We report on the formation of concentric rings within the bulk of cellulose films after laser machining with high energy femtosecond laser pulses. The rings originate from an interference effect, where the front of the pulse is reflected from the back surface of the sample and interferes with its tail. Ray tracing simulations confirmed the interference and rings formation. Modification at the back surface of materials may go unnoticed and lead to undesired properties. These findings are therefore important for the ultrafast laser community interested in machining of transparent materials.

Fate Restriction and Multipotency in Retinal Stem Cells

Stem cells have the capacity to both self-renew and generate postmitotic cells. Long-term tracking of individual clones in their natural environment constitutes the ultimate way to validate postembryonic stem cells. We identify retinal stem cells (RSCs) using the spatiotemporal organization of the fish retina and follow the complete offspring of a single cell during the postnatal life. RSCs generate two tissues of the adult fish retina, the neural retina (NR) and the retinal-pigmented epithelium (RPE). Despite their common embryonic origin and tight coordination during continuous organ growth, we prove that NR and RPE are maintained by dedicated RSCs that contribute in a fate-restricted manner to either one or the other tissue. We show that in the NR, RSCs are multipotent and generate all neuron types and glia. The clonal origin of these different cell types from a multipotent NSC has far-reaching implications for cell type and tissue homeostasis.

Assembly of nanoparticles at the contact line of a drying droplet under the influence of a dipped tip

The manipulation of colloidal nanoparticles (NPs) in a drying droplet has critical importance not only for several industrial applications but also their assembly into patterns on surfaces. The influence of a tip with hydrophilic or hydrophobic surfaces dipped into a drying droplet on hydrophilic or hydrophobic surfaces on the behavior of 98nm latex NPs was investigated. The formation of concentric rings on hydrophilic glass surfaces regardless of the surface chemistry of the dipped tip was observed. On the other hand, no pattern formation on hydrophobic surfaces was observed with the insertion of the tip. With a hydrophilic tip, the concentric rings were formed due to stick–slip motion of the solvent contact line resulting from competition between pinning and capillary forces while the capillary effect was not effective until the surface of the tip was changed by adherent NPs making the tip surface available for water adherence with a hydrophobic tip, which results in the pulling of droplet towards the tip. It is also found that the tip thickness and suspension concentration significantly influences the formation of concentric rings on surfaces. This simple procedure can be used to influence the distribution or assembly of NPs in the droplet area.

Controlled evaporative assembly of polymers from confined solutions

INTRODUCTION In the process of drying, nonvolatile solutes (e.g., polymers, proteins, viruses, bacteria, DNA, microspheres, nanocrystals, carbon nanotubes, etc.) contained within a sessile droplet (i.e., unconstrained liquid) readily assemble into a diverse range of intriguing oneor two-dimensional structures, possessing dimensions of a few hundred submicrons and beyond. It is, in principle, a nonequilibrium process. Two main characteristic patterns are often observed: ‘‘coffee rings’’ and irregular network structures (i.e., Benard cells). A ‘‘coffee ring’’ forms when, in the absence of natural convection and surface tension gradients, the contact line of an evaporating drop becomes pinned. This ensures that liquid evaporating from the edge is replenished by liquid from the interior, so the outward flow carries the nonvolatile dispersions to the edge. The evaporation flux varies spatially, with the highest flux observed at the edge of drop. A subset of the ‘‘coffee rings’’ phenomenon is the formation of concentric rings by repeated microscopic pinning and depinning events (i.e., ‘‘stick-slip’’ motion) of the three-phase contact line, that is, the competition between the friction force and surface tension of the solution. However, random concentric rings are generally formed. Moreover, based on Navier-Stokes equations with a lubrication approximation, the bulk of current theoretical work has centered on understanding a single ring formation using either analytical or numerical methods. By contrast, only a few elegant theoretical studies have focused, either analytically or numerically, on the formation of periodic multirings (i.e., concentric rings) during droplet evaporation on a substrate. A gradient of temperature normal to the droplet surface due to solvent evaporation can induce a Marangoni-Benard convection (i.e., closed-loop circular convection), which results in irregular Benard cells caused by the upward flow of lower, warmer liquid. The spatial variation of evaporative flux and possible convection mean, however, that these nonequilibrium, dissipative structures (e.g., ‘‘coffee rings,’’ cellular structures, fingering instabilities, etc.) are often irregular and stochastically organized.

The effects of normal current density and the plasma spatial structuring in argon DBDs

This paper presents the results of theoretical studies of high-pressure dielectric barrier discharges (DBD) in argon. Two different DBDs at the megahertz and the kilohertz power frequency range were simulated. The effect of normal current density was obtained in the numerical model for both types of the discharge. The discharge of megahertz range was uniform over the radius. The increase in the discharge current is accompanied by increase in the discharge area. The discharge of kilohertz range is not uniform over the radius. The concentric ring formation was observed during calculations. The increase in the discharge current occurs due to increase in the number of rings and as a result in the discharge area. The developed 2D model is able to describe only the first stage of the filament formation – the formation of concentric plasma rings. The filament formation starts at the edge of the current channel and spreads to its centre. Both the effect of normal current density and the filaments formation are caused by the nonstationarity at the current channel boundary.

Ultrasonic parametric imaging of erythrocyte aggregation using the structure factor size estimator

Ultrasound characterization of erythrocyte aggregation (EA) is attractive because it is a non-invasive imaging modality that can be applied in vivo and in situ. An experimental validation of the Structure Factor Size Estimator (SFSE), a non-Rayleigh scattering model adapted for dense suspensions, was performed on 4 erythrocyte preparations with different aggregation tendencies. Erythrocyte preparations were circulated in Couette and tube flows while acoustically imaged over a bandwidth of 9-28 MHz. Two acoustically derived parameters, the packing factor (W) and ensemble averaged aggregate size (D), predictably increased with increasing EA, a finding corroborated by bulk viscosity measurements. In tube flow, a "black hole" reflecting the absence of aggregates was observed in the center stream of some parametric images. The SFSE clearly allowed quantifying the EA spatial distribution with larger aggregates closer to the tube walls as the aggregation tendency was increased. In Couette flow, W and D were uniformly distributed across the shear field. Assuming that the viscosity increase at low shear is mainly determined by EA, viscosity maps were computed in tube flow. Interestingly, erythrocyte suspensions with high aggregabilities resulted in homogeneous viscosity distributions, whereas a "normal" aggregability promoted the formation of concentric rings with varying viscosities.

Formation of calcium oxalate concentric precipitate rings in two-dimensional agar gel systems containing Ca 2+–RE 3+ (RE = Er, Gd and La)–C 2O 42−

The concentric precipitate rings are found in urinary stone section and may relate to Liesegang pattern and formation mechanism of urinary stone. Urinary stone is mainly composed of calcium oxalate, so it is significant to study the concentric precipitate rings. The influence of RE 3+ on the formation of calcium oxalate concentric precipitate rings is studied for the first time in two-dimensional agar gel systems. Precipitate rings are characterized by means of Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and biomicroscope with digital camera. The results show concentric precipitate rings are made of calcium oxalate and RE 3+ promote the present of rings. The number of concentric rings are influenced by different RE 3+ and the reaction time. The agar gel systems are helpful for the ions to diffuse uniformly, and as a medium where calcium oxalate rings are formed. In comparison with Gd 3+ and La 3+ ions, the content and size of calcium oxalate monohydrate (COM) crystals are highest and biggest after the addition of Er 3+ ions, indicating that Er 3+ ions promote the formation of concentric rings effectively. However, in the similar systems containing Cu 2+, Fe 2+, Fe 3+and Co 2+, we found the ring only appeared in the system containing Fe 3+ ions. And the formation mechanism of the calcium oxalate concentric precipitate rings in two-dimensional agar gel systems containing rare earth ions is also discussed in the paper.

Formation of concentric rings of antiparallel domains in the nonlinear-optical ferroelectrics in the presence of an HF field

The formation of cylindrical antiparallel domains is predicted for ferroelectrics in the presence of an HF field at a constant bias. The reorientation of the domains on the temperature lattice induced by the HF field whose amplitude is described with the zero-order Bessel function is considered. The quasi-period of the antiparallel domains is estimated for LiNbO3, LiTaO3, and Ba0.5Sr0.5Nb2O6 crystals. The phenomenon can be used to create photonic crystals, in particular, for the spatial selection of optical signals based on the controlled electrooptical reflection.

Edematous Schmorl’s nodes on thoracolumbar MR imaging: characteristic patterns and changes over time

To describe the patterns and note the evolution of edematous Schmorl's nodes. In 47 patients (M:F=26:21, 24-86 years, average 60), 84 Schmorls nodes with T2 hyperintensity with serial MR exams were evaluated. Interval between MR exams was 2-72 months (average 17). Two observers noted size, location, margins, internal and surrounding T1/T2 signal, adjacent disc herniation or bulge, concentric ring, underlying fracture, malignancy, infection, or prior disc surgery, and serial MR changes in these characteristics over time. Node size averaged 7x9 mm. Most were located at L3 (29%, 24/84), L4 (19%, 16/84) and L2 (13%, 11/84), at the central (39%, 33/84) or outer (30%, 25/84) third of the endplate. 55% (39/71) had a bulging disc, 7% (5/71) had disc herniation. 10% (8/84) had evidence of associated fracture, 17% (14/84) tumor, 7% (6/84) infection. Most nodes had well-defined margins (82%, 69/84). The most common node internal signal was isointense to adjacent disc on T1/T2 (33%, 28/84); surrounding marrow was most commonly hypointense on T1 and hyperintense on T2 (54%, 38/71). A common finding was concentric rings (38%, 32/84) in the marrow surrounding the node, a finding which had 72% negative predictive value for absence of infection, tumor and fracture. On follow-up, there was no interval change in node size in 46%(39/84) of Schmorl's nodes. 26% (22/84) had increased size. Most (60%, 50/84) showed no temporal change in internal T2 signal. 21% (18/84) of nodes showed decreased internal T2 signal, 13% (11/84) showed increased T2 signal. Regarding the surrounding marrow, most (58%, 49/84) showed no temporal change in T2 signal; 21%(18/84) showed decreased T2 signal, 13% (11/84) showed increased T2 signal. In 13 Schmorl's nodes with intranodal enhancement, eight (62%) showed no interval change; among eight with enhancement in surrounding marrow, five (63%) showed no change on follow-up. Although most remain unchanged, a relatively large minority of edematous Schmorl's nodes evolve in size and signal over a relatively short time. Some evolve to form well-defined concentric rings in the surrounding marrow that appear to be analogous to degenerative changes of endplates. Concentric ring formation has a high negative predictive value for "idiopathic" Schmorl's nodes without underlying fracture, infection, or malignancy.

Periodic growth of bacterial colonies

The formation of concentric ring colonies by bacterial species Bacillus subtilis and Proteus mirabilis has been investigated experimentally, focusing our attention on the dependence of local cell density upon the bacterial motility. It has been confirmed that these concentric ring colonies reflect the periodic change of the bacterial motility between motile cell state and immotile cell state. We conclude that this periodic change is macroscopically determined neither by biological factors (i.e., biological clock) nor by chemical factors (chemotaxis as inhibitor). And our experimental results strongly suggest that the essential factor for the change of the bacterial motility during concentric ring formation is the local cell density.

Formation of Concentric Rings Around Sources

Zones of increased concentration formed by a solvent flowing from a source are considered. A matehmatical model for forming such zones is proposed. It takes into account that such a zone is composed of a set of independent particles. Hence the distribution of a substance around the source can be explained by movement of an individual particle. In the model this movement is a continuous semi-Markov process with terminal stopping at some random point in space. Parameters of the process depend on the velocity field of the flow. Forward and backward partial differential equations for the distribution density of a random stopping point of the process are derived. The forward equation is investigated for the centrally symmetric case. Solutions of the equation demonstrate either a maximum or a local minimum at the source location. In the latter case a concentric ring around the source is formed. If different substances vary in their absorption rates, they can form separable concentration zones as a family of concentric rings.

Pattern formation in the crystallization of ascorbic acid

It is well known that ascorbic acid exhibits various patterns when it crystallizes from its methanol solution. In this article, we present an experimental and a theoretical study of the pattern formation, especially concentrating on the formation of concentric rings caused by the oscillatory crystallization. The void-fluid interaction will be proposed as a mechanism which will be responsible for the oscillation.

Formation of concentric rings on the flaked surface of Mylar due to 250-keV H+-ion implantation.

Formation of concentric rings on the flaked surface of Mylar due to 250-keV H+-ion implantation.